Segments and Geographic Data - Summary of Operating Performance and Assets by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 03, 2021	Dec. 29, 2019	Dec. 30, 2018
Segment Reporting Information [Line Items]
Consolidated revenue	$ 3,239	$ 3,543	$ 3,333
Consolidated depreciation and amortization	187	188	179
Consolidated income from operations	580	985	883
Consolidated total assets	7,585	7,316	6,959
Consolidated capital expenditures	189	209	296
Core Illumina
Segment Reporting Information [Line Items]
Consolidated capital expenditures	189	209	294
Helix
Segment Reporting Information [Line Items]
Consolidated capital expenditures	0	0	2
Operating Segments | Core Illumina
Segment Reporting Information [Line Items]
Consolidated revenue	3,239	3,543	3,334
Consolidated depreciation and amortization	187	186	175
Consolidated income from operations	580	1,008	970
Consolidated total assets	7,585	7,316	6,912
Operating Segments | Helix
Segment Reporting Information [Line Items]
Consolidated revenue	0	1	10
Consolidated depreciation and amortization	0	3	6
Consolidated income from operations	0	(24)	(90)
Consolidated total assets	0	0	154
Eliminations
Segment Reporting Information [Line Items]
Consolidated revenue	0	(1)	(11)
Consolidated depreciation and amortization	0	(1)	(2)
Consolidated income from operations	0	1	3
Consolidated total assets	$ 0	$ 0	$ (107)